Silencer for telephones and the like



Dec. 1 ,"1925- 1,563,586

A. N. PIERMAN ET AL smancna FOR wmrnouss AND THE LIKE Filed Jan. 22, 1924 S b m H J N mi N E r R v.6 0 ma w f m 5 CA am m 3% 5 Patented Dec. 1, 1925.

UNITED STATES PATENT OFFICE.

ALEXANDER N. PIERIVIAN, OF NEWARK, AND NATHAN A. CURTISS, OF RAMSEY, NEW JERSEY, ASSIGNOBS TO MILLER REESE HUTCI'IISON, OF NEW YORK, N. Y.

SILENCEB FOR TELEPHONES AND THE LIKE.

Application filed January 22, 1924. Serial No. 687,693.

Tortilla/10m it wi l concern Be it known that we, Ari-manner. N. PinniMAh and Nari-nix A. Cnirriss, citizens of the ignited States, and residents, respectively, of he ark, in the county of Essex and State of New Jersey, and of Ramsey, in the county of Bergen and State of New Jersey, have invented certain new and useful Improvements in Silencers for Telephones and the like, of which the following is a specification.

Our invention is shown as embodied in a telephone silencer of a type set forth in the application of Miller Reese Hutchison, executed Januar 5th, 192%, and filed January ill. 192i. Viiile the novel features herein disclosed are shown in combination with certain features of said Hutchison application and while said.novel features are particularly adapted for use in such combination, they are also useful in other relations.

Our device comprises a sound and draft transmitting conduit which has breather vents opening into a breather silencer which preferably surrounds and is mounted on said conduit. As in the Hutchison device, this conduit may be a sound collector in the form of a cylindrical tube of proper diameter for fitting the mouthpiece of a telephone transmitter and may be contoured at the outer end to fit the mouth or both mouth and nose of the speaker. The purpose of the breather silencer is to permit through draft of air with as little resistance as possible consistently with the main purpose which is baffling, mu'l'tling and confusing sound waves so as to greatly decrease their intelligibility. Where the purpose is to permit breathing by the user, small volume and short length of the battling labyrinth is also desirable to minimize the amount of exhausted breath that must. be churned back and forth in order to draw in a desired amount of fresh air.

in the primary form of the Hutchison silencer, these purposes are served by a construction wherein concentric cylinders are used as the partitions forming the passages between bafliing points; the pathfor the breath and the sound waves is straight back and forth parallel with the axis of the tubes; and the effective width, that is,the circumference of the annular passages must be greater than that of the collector tube which is inches or more. In practice these prin-iar3-* limitations result in many other limitations which it is the object of our inven' tion to avoid.

The primary feature of our invention is that we form the partitions forthe labyrinth edgewise about the cylinder instead of parallel therewith. Preferably they are integral with the cylinder and are closed in circumferentially by a sheet metal cylinder accurately fitting the tops of the tubes. The edgewise arrangement gives complete flexibility for the designer. The partitions may be as near together or as far apart as desired. They may be annular or longitudinal or preferably both. Preferably the guiding partitions are in radial planes at right angles to the axis of the main tube and the battling partitions are lengthwise of the tube, openings through the partitions being arranged so that the waves travel'circumferentially between battling points. If desired, however, and, particularly for other purposes, it is possible to arrange for the guiding partitions to be longitudinal and the battling partitions circumferential.

In either case there is ample room to'make the partitions as thick as may be necessary to prevent vibration and conduction by the walls of the device. The cross-sectional area of the passages and alsothe ratio of their height to width may be widely varied without any of the above referred to limitations attendant upon the use of concentric cylinder partitions.

Vith radial partitions spaced only two to the inch, there is room on the telephone mufiier for at least five of the circumferential passages for the waves and if the muffler is three inches in diameter, the aggregate length of these passages will be, say, 40 inches as against the 12 inches described above as available in the Hutchison device. Moreover, the passages being curved, the the waves tend to follow the outer side of the curve and this affords an effective friction surface which the straight moving waves are continuously impingin This is particu larly effective in wearing out and destroying the high frequencies upon which the intelligihility of voice sounds depends.

The above etiiciencies are such that we find it isperfectly practicable to have two diametrically opposite sets-0f battling partitions and corresponding outlets dividing the total available space into two entirely separate paths for the Waves. The amount of energy in each path is only half as much but the number of bafliing points is the same. Moreover, the effective acoustic length be tween bafiiing points is approximately four inches or the total length from the inlet to the outer air is eighteen inches or more. These lengths are of acoustic importance because it permits quarter waves of many of the more important frequencies of speech to be contained within the space between baffling points, while half waves and even entire waves of the lower frequencies are con tained within the total length of the device. Both of these features seem to be of advantage as regards the effectiveness of reflections occurring at the baffling point and also as regards tendency to reduce vibration of the device or parts thereof such as can be communicated to the telephone transmitter to repair purity of transmission there- 'hrough.

Another important feature is that both guiding partitions and baffling partitions being radial, it becomes practicable to die cast said partitions integral with the main tube and with the nosepiece, if the latter is used.

The above and other features of my invention may be readily understood from the following description in connection with the accompanying drawings, in which Fig. 1 is aside elevation of the complete device, with the outer cylinder broken away to diametric section;

Fig. 2 is a rear end elevation;

F 3 is a characteristic cross-section showing a modification.

In these drawings the conduit 1 for receiving the air pressures and sound waves is a tube adapted to fit over the mouthpiece of a telephone transmitter. lVhen used for this specific purpose, the tube may be contoured as at 2 and maybe provided with a nose shield 3 to fit the face of the user; also it may be securedto the telephone transmitter by an abutment flange 8 covered with cushioning material 9 against which the front edge of the telephone mouthpiece is held by forwardly directed springs 12 secured at the rear end by screws 13, each spring and the screw held being preferably countersunk in a recess as shown.

The tube 1 is provided with a lateral vent 16 of ample outlet area for escape or inlet of the air in response to the varying pressures. Such vent also permits escape of the sound waves and the silencer formuflling these and,'in the case of voice waves for rendering them unintelligible, comprises radial D -9 c ud ng end walls 17, 1S and in termed ate guidingpartitions 19, 20, 21 and 22; which are. preferably in parallel planes at right angles to the axis of the tube 1. and preferably are equally spaced. I

The annular spaces i between partitions communicate through openings as 29, 30, I31 and 32which are so arranged that the air draft and sound waves must traverse relatively long circular paths in the interspaces in order to escape through the successive openings. 7

Preferably each annular space is baffled by a transverse or bulkhead partition and this may be accomplished for all of said spaces by a single longitudinal partiton 40. The partition affords impact surfaces which tend to baflie the sound waves but afford very little resistance to the air drafts which are air currents that flow around the curves at speeds much slower and for periods almost incon'iparably longer than the air movements constituting the movement phases of the sound waves.

If desired, one or more of the baffling partitions may be arranged to constitute walls of the openings through the guiding parti tions, and as shown in Fig. 1, the area of the opening is preferably the same as the crosssectional area of the annular spaces which are connected thereby.

The outer edges of the partitions are preferably f'ormed as elements of a true cylin tier so that the annular spaces, as also the openings between the partitions, can be closed in by cylindrical tube 50 which may be applied by sliding it endwise over the partitions.

As indicated in Fig. 2, the air draft and remnants of sound if any, escaping from the outlet 32, traverse an approximately com plete circle betweenpartitions 22 and endwall 18, escaping through outlet holes 56. These holes are preferably below tube 1, which tends to shield the remnant of sound from bystanders. A slot could be used, but a plurality of distributed holes have a slightly better effect in confusingand mufliing the sound.

While the above device could be constructed from tin or sheet lead, it is preferably made of metal so heavy as not to vibrate material.- ly either as a whole or in any of its parts, in response to any resonance effects that may be set up by the sound waves within the cavity. For telephone purposes this is important, because in spite of the use of springs 12 and cushion surface 9, vibrations such as are producible in thin spring metal walls, can be communicated to the microphone ot the transmitter, thereby impairin the clear ness of the transmission.

Such thick metal walls can be built up from heavy drawn tubing which serves for conduit 1, and enclosing cylinder 50. and

from heavy rolled sheet brass which serves for the partitions. For quantity production, however, this is expensive and as before. ex plained, an important advantage of the radial partitions is that it permits of die cast ing in one piece of-the tube 1 with itsv inter.-

nal abutment flange 9, its external parti tions, and the vent slot 16.

Such casting requires only litting of the cylinder 50 in order to complete the essential working parts of the device. If'the -external cylindrical contour of the die casting is not sutiicientlyaccu ate, or if a sand casting is used, it is a'simple matter to ma chine the outer edges of the-partitions to the true-cylinder contour. v

As before explained, the above construction ati'ords three or four feet of battling passages and experience indicates that there is advantage in utilizing the space for two parallel passages in which the air and waves traverse semi-circles, instead; of contiplete circles, bet-ween battling points. This requiies only the use of two transverse partitions as 50, 50", Fig. 3, with two corresponding sets of openings in the successive guide partitions, as 29, 29 for partition 19" and 30, 30" for the next partition; also two vent slots, as 16, 16", for tube 1. In this modification the two t'ansverse partitions 50" may be in the vertical longitudinal. plane'of the device and the openings in the partitions may be recessed inward from the periphery along lines perpendicular to said partitions. This facilitates die casting since it permits of an exterior mold made in two sections, contoured so as to have proper draft lines of withdrawal from the complete casting, in directions perpendicular to the partitions.

As before noted, the simple construction problems presented in the foregoing remain the same for all thicknesses, spacings,lengths and cross-sectional areas for the walls, inter-spaces and openings. Hence the designer is free to vary these widely to get desired results in the telephone silencer or to adapt the silencer for air drafts other than the breath and sound waves of the voice.

The device may be made of other mate rials, as aluminum or aluminum alloy, hard rubber or even celluloid, although the latter is likely to be vibratory unless the walls are of ample thickness.

The device is shown as designed so as to slip over and off of the mouthpiece of aregular telephone transmitter, but, so far as concerns certain of the novel features, the rear end could be made a proper size and externally screw-threaded to screw into the front plate of the transmitter casing, as a substitute for the regular mouthpiece. Similarly, the device is shown as having the main conduit, 1, a true cylinder and the nosepiece joining the same by reentrant curves, but so far as concerns the novel features of the silencing labyrinth, said main conduit could be more or less conical or curved longitudinally and could be polygonal or even square or triangular in cross section. lvloreover, so far as concerns these features, the vents from the main conduit to the silencing labyrinth need not discharge radially since the waves would be almost if not'quite as well battled if they entered the first annular passage in a direction parallel with the main conduit, as for instance a through the front end radial flange.

It is to be noted that the labyrinths as designed are intended to battle incoming drafts and sound waves as well as outgoing drafts and sound waves. Hence they may be designed to have the primary conduit associated with what are now the outlets, in which case the present outlets would serve as inlets and the present vent passages would become the outlets.

We claim:

1. A tubular conduit having a vent for vair pressures and sound waves and, in receiving relation to the vent, silencer passages including radially extending partitions arranged edgewise on the exterior of said conduit, some of said partitions being circumferential and others longitudinal.

2. A tubular conduit having a vent for air pressures and sound Waves and, in receiving relation to the vent, silencer passages including radially extending guiding partitions and battling partitions arranged edgewise on the exterior of said conduit.

3. A tubular'conduit having a vent for air pressures and sound waves and, in receiving relation to the vent, silencer passages including radially extending guiding partitions and bathing partitions arranged edgewise on the exterior of said conduit, the guiding partitions being parallel and having openings connecting the interspaces between them.

4. A tubular conduit having a vent for air pressures and sound waves and, in receiving relation to the vent, silencer passages including radially extending guiding partitions and baffling partitions arranged cdgewise on the exterior of said conduit, the guiding partitions being parallel and havin openings connecting the interspaces between them and the openings through the guiding partitions being adjacent the baffling partitions.

5. A tubular conduit havin a vent for air pressures and sound waves and, in receiving relation to the vent, silencer passages includ ing radially extending guiding partitions and battling partitions arranged edgewise on the exterior of said conduit, said guiding partitions being in parallel planes at right angles to the axis of said conduit.

6. A silencer for telephone transmitters, including a tubular portion having breather vents between the month end and the transmitter end and radially extending partitions at the exterior of said tubular portion having their edges in contact therewith and means cooperating with the partitions to provide silencing passages disposed so that the breath currents and the sound waves t'averse to and fro paths, circumferentialljy of said tubular portion, alternately in opposite directions.

7. A silencer con'iprising a tubular portion having breather outlets and formed externally with radial partitions having outlet openings forming zig-Zag passages with impingement surfaces at the ends of the passages, together with a surrounding tube fitting the peripheral edges of Said partitions and forming peripheral walls of said passages.

8. The silencer specified by claim 7. with the further feature that the passages between the partitions communicate through open indentations in the peripheral edges of the partitions so that the surrounding tube also forms. an outer wall for said indentations.

9. A silencer comprising a tubular portion adapted to fit over the mouthpiece of a telephone transmitter and formed in advance of said mouthpiece with breather outlets and formed externally with edgewise partitions having outlet openings; and an exterior tube fitting over the outer edges of said partitions to form zig-zag passages having terminal impingement surfaces.

10. Anintegral casting comprising a tubular portion having one end adapted to fit a telephone transmitter, said tubular portion being formed with breather outlets and formed externally with molded radial partit-ions, some circumferential and some transverse, and having cylindrical outer edges engaged and closed in by a surrounding cylinder, to form battling passages for sound waves and for flow of air.

11. An integral casting comprising a tubular portion having one end adapted to fit over the mouthpiece of a telephone trans mitter, said tubular portion being formed in advance of said mouthpiece with breather outlets and formed externally with radial annular partitions forming communicating passages, having cylindrical outer edges adapted to be engaged and closed in by a surrounding cylinder.

12. A tubular conduit adapted to fit over an d surround a telephone transmitter mouthpiece, in combination with a silencer passage for breathing purposes, comprising radially disposed guiding partitions and battling partitions arranged edgewise on the exterior of said conduit.

Signed at New York, in the county of New York and State of New York, this 21st day of January, A. D. 1924.

ALEXANDER N. PIERMAN NATHAN A. CURTISS. 

